Filter products typically include a quantity of filtration media and a frame that is not only sized and shaped to partially enclose and support the filtration media, but also sized and shaped so that the filter product can be inserted or supported in place based upon a particular application. Conventionally, filter frames have been constructed from multiple elements that are assembled together or connected to the filtration media, such as about its perimeter, so as to provide the support and application-specific filter frame. Such frame elements are known to be made from a variety of materials, including metals, plastics, and paperboard. In the case of a rectangular filter product, for example, a rectangular filtration media is surrounded at its four sides by frame pieces that may be connected at the corners and/or connected to the four side edges of the filtration media. The majority of the filtration media is thus capable of use for its filtering ability.
Moreover, these typical frame elements comprise three-dimensional elements that are sized and shaped to partially enclose the filtration media at its edges. The frame may comprise multiple pieces assembled by use of adhesive, welding, friction fit, snap fits, mechanical fasteners, or like. Otherwise, the entire frame or any selective portion thereof may be made integral. That is, a frame portion comprising multiple elements made together may be provided, such as, for example, by an injection molding process. In any case, the one or more frame elements must be assembled and connected with the filtration media by a selective assembly process. Such a selective assembly process requires manipulations of the elements for assembly. A selective assembly process, as used herein, is contrasted with an in-line process where elements are brought together in a continuous manner from materials of indefinite length and by which at least an intermediate product combining the continuous materials is created. By indefinite length, it is meant that a material may be provided in many different supply forms, such as, for example, in roll form, but in any case where the length of material supplied is not specifically related to the length that would be needed for a single product application.
Many types of filter products have also been developed for many different types of applications. Applications often are based in large part upon the characteristics of the filtrate and the carrier fluid and upon the support requirements of the system of the particular application. Filtering requirements may make it necessary to construct the filter products under construction specifications that ensure that all carrier fluid and filtrate must pass through the filter product. This may require appropriate sealing mechanisms between the frame and its system support, for example by one or more gaskets, and between the frame and the filtration media, for example by adhesive sealant. Such adhesive sealant may be provided as a bead extended along the entire frame at an interface between the frame and the filtration media. For example, a typical high-efficiency particulate air (HEPA) filter uses pleated filtration media sealed about its edges to a frame that is provided about its complete perimeter. Thus, the filtration media and frame provide a fluid tight assembly that prevents bypass of unfiltered carrier fluid.
A continuous strip of framing material that can be manufactured as an indefinite length and converted into a filter frame is disclosed in the PCT International Application publication number WO 01/02080A1, published Jan. 11, 2001. Specifically, a continuous strip framing blank can be made by extrusion, the framing blank having a sidewall portion and plural tabs that extend from the sidewall portion to create a u-channel of indefinite length. This channel is then notched at its tabs to form corners that may further be scored to permit easy bending of the channel at corners of the filtration media, which media may comprise a pleated filtration media or other flat media of a shape such as a rectangle. An important aspect of the continuous strip of framing blank material is that it may be made by co-extrusion techniques so that different portions of the framing blank material may have different characteristics. For example, the framing blank material may also include seal enhancement features of a much more flexible nature than the frame sidewall and tabs, which combination of features may be made by coextruding different polymeric materials together having appropriate characteristics. To assemble such filter, the continuous strip framing material is cut into discrete frame blanks with predetermined corners and the frame blanks are wrapped about filter media with an adhesive potting compound at an interface between the filter media and the frame channels.
However, in addition to improving the ability to make a continuous framing material, it is also desirable to more effectively store and supply the continuous framing material and assemble framing material to the filtration media by a continuous in-line process. In the case of the continuous strip of framing blank material of the above copending case, the channel structure of the framing material makes it difficult to create a supply form of the framing material capable of providing an indefinite length of material of a significantly greater length than that required for individual cases, such as would be obtainable if the material could be wound into a roll form.